1. Field of the Invention
The present invention relates to a communication system and a communication method which are suitable for being applied to a system including a device that performs an input or output in conformity with a digital video/audio I/O interface standard called the HDMI (High-Definition Multimedia Interface) standard, and relates to a video output apparatus and a video input apparatus which are used in the system.
2. Description of the Related Art
Lately, the HDMI standard has been developed as an interface standard to transmit uncompressed digital video data and the like between a plurality of video apparatuses. According to the HDMI standard, video data is transmitted as individual primary color data respectively transmitted by one pixel. In the HDMI standard, audio data is also transmitted using a transmission line for the video data in a blanking period of the video data. Primary color data of red, green and blue (R-data, G-data, and B-data) are transmitted as the primary color data. Luminance and color-difference signals such as Y, Cb and Cr may be transmitted instead of the primary color data.
According to the HDMI standard, one pixel data of respective colors is basically transmitted by eight bits. Synchronization signals such as a horizontal synchronization signal and a vertical synchronization signal are also transmitted at a timing that each synchronization signal is arranged. A video data transmission line using pixel clock and a control data transmission line are provided. Since uncompressed digital video data is transmitted by a pixel as described above, a high definition video data and the like can be transmitted while copyright is protected.
A plurality of video apparatuses such as a video signal source device, for example, a disk reproduction apparatus, and a display apparatus (monitor receiver, television receiver, and the like) are typically connected using the transmission line (HDMI cable) of the HDMI standard. A device that outputs video data and the like to the transmission line of the HDMI standard is called a source device (output apparatus), and a device that inputs the video data and the like via the transmission line of the HDMI standard is called a sink device (input apparatus).
WO2002/078336 discloses a detailed description of the HDMI standard.